1. Field of the Invention
The invention relates to electronic device processing equipment. More particularly, the invention provides an electrical coupling between a fixed chamber part (such as a chamber liner or chamber wall) and a movable chamber part (such as an element of a movable electrode assembly) to reduce differences in the electrical potential of such parts and prevent or reduce the presence of excited gases or plasma in undesired regions of the processing equipment.
2. Discussion of Background
Various types of processing equipment are utilized in the manufacture of electronic devices such as semiconductor devices or panels used in liquid crystal displays. For example, deposition equipment is utilized for depositing films or layers upon a semiconductor wafer. xe2x80x9cEtchersxe2x80x9d typically utilize a plasma to remove or etch portions of a film or layer from a wafer to form the desired features or devices upon the wafer. Due to the extremely small size of the features formed in semiconductor processing, the processing equipment must be carefully and precisely controlled. The equipment usually includes a xe2x80x9cchamberxe2x80x9d or enclosed region, within which the environment is controlled for optimal processing of the wafers.
In electronic device processing equipment, electrodes are utilized to control the environment within the process chamber. For example, etchers typically utilize electrodes to excite the process gases into a state known as a xe2x80x9cplasma.xe2x80x9d The plasma performs a process upon the wafer, e.g., to deposit a layer on the wafer or to etch the wafer, and the process gases (and byproducts) are then exhausted from the chamber.
There are various chamber and electrode configurations in electronic device processing equipment. One known plasma etcher arrangement includes parallel upper and lower electrodes. The upper electrode is grounded, and radio frequency power is applied to the lower electrode to strike and maintain a plasma between the upper and lower electrodes. Depending upon the geometry and other factors, the plasma in this type of an arrangement can also be coupled to a grounded chamber wall (and/or the liner of the chamber wall if a liner is provided) such that the upper electrode and chamber wall, in effect, form the ground electrode. Many other process chamber configurations are also known. For example, certain etchers include more than one powered electrode.
Regardless of the particular configuration, the electrodes are extremely important components in controlling the process performed within the chamber. Other components within the chamber are also needed, which are not intended to play a role in striking or maintaining a plasma or otherwise controlling the process to be performed. However, although certain chamber parts are not intended to play a role in controlling the process, an electrical potential difference sometimes can occur between such parts (or between such non-electrode parts and electrode parts). These unintended and undesirable potential differences can have a number of deleterious effects. For example, an unintended potential difference could cause a plasma or excited gases to be present in unintended regions of the chamber. This plasma can adversely effect the plasma (or the control of the plasma) in regions of the chamber in which plasma is intended to be present. For example, the properties and performance of the plasma in the chamber can be affected if the plasma should become coupled to parts in unintended/undesirable regions of the chamber. The unintended/undesired plasma or excited gases could also cause the etching or wear and premature failure of the chamber parts. Moreover, the etching of such parts can generate particles, introducing impurities onto the surface of the wafer. Deposits on the chamber parts can also generate particles when the deposits are subsequently dislodged.
The present invention provides an arrangement which can reduce the presence of plasma or excited gases in regions of a chamber for which such plasma or gases are not desired or intended. The present invention can also reduce the adverse effects such plasma or gases can cause.
In one form of the invention, an electrical coupling is provided between chamber parts to eliminate or at least reduce differences in the electrical potential between such parts, thereby reducing the possibility that plasma (or excited gases) will be formed, sustained or have undesirable effects. By way of example, in an illustrated embodiment, an improved electrical coupling is provided in a two electrode etcher assembly having a powered movable lower electrode assembly and a ground upper electrode. The movable electrode assembly includes parts which are insulated from the powered electrode, and which are not intended to be powered or to have a potential difference with other grounded parts of the chamber, such as the grounded chamber wall. However, it has been found that potential differences between parts of the lower electrode assembly and the chamber wall can occur, and can result in the presence of excited gases or a plasma in undesirable regions of the chamber. Potential differences can assist in drawing plasma or excited gases created in other regions into the undesirable or unintended regions, or the potential differences could cause the formation of a plasma or excited gases in the undesirable regions. In either case, it has been recognized in accordance with the present invention that, by providing an electrical coupling between the chamber parts, such as parts associated with the movable electrode assembly and parts associated with the chamber wall, the undesirable presence of plasma or excited gases can be prevented or reduced. The terms xe2x80x9cplasma or excited gasesxe2x80x9d are used herein since excited gases can sometimes be present and have characteristics associated with a plasma (e.g., emitting light) although such gases are not always truly a plasma.
In one form of the invention, the electrical coupling extends between a first chamber part which is fixed and a second chamber part which is movable. In the illustrated embodiments, the first chamber part is an unpowered part of a movable lower electrode assembly, and the second chamber part is a chamber liner which lines the wall of the chamber. The electrode assembly is movable so that in an upper or raised position, the lower electrode is properly positioned for processing the wafer. The electrode assembly is lowered when a process is not being performed to allow placement of a wafer upon the electrode or removal of a processed wafer from the electrode. The electrical coupling includes a yieldable portion, such as a flexible portion or spring biased portion, such that the electrical coupling can be urged or biased toward the second or fixed chamber part to ensure contact when the lower electrode assembly is in its raised or operational position. Although the illustrated embodiments provide an electrical coupling between part of a movable electrode assembly and a chamber liner in an etcher having a single powered electrode, as discussed in further detail herein, the invention can be advantageously utilized in various types of electronic device processing equipment and to couple various parts to reduce potential differences which could be present between such parts.